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Lennart Grimm

“Understanding changing landscapes by measuring isotopes produced by cosmic radiation”

PhD project title:

Signals of landscape transience in detrital cosmogenic nuclides

Project description:

Lennart Grimm PhD student
The analysis of cosmogenic nuclide (CN) concentrations in fluvial sediments is a widely used method for estimating catchment-averaged denudation rates. A fundamental assumption of this approach is that all parts of the landscape contribute equal amounts of material to the catchment’s outlet and that erosion and uplift throughout the catchment are in balance such that a steady state is reached.

However, changes in external forcings such as uplift and climate will cause landscapes to adjust their river channels and hillslopes before reaching a renewed equilibrium. As the Quaternary Period has been marked by fast cyclic variations in climate, few landscapes can be assumed to be in true steady state, violating an important premise of CN-based denudation rate calculations.

This project aims to quantify effects of landscape transience on CN-based catchment-averaged denudation rates and to develop new methods to gain additional insights into transient landscape processes from CN analyses. Applying lessons learned from detrital thermochronology, we will investigate in-situ cosmogenic 3He populations in transient and equilibrium landscapes to estimate the reliability of catchment-averaged denudation rates calculated from CNs. Additionally, we will compare such distributions to published cooling age distributions from thermochronological studies and explore how our findings can be used to deepen our understanding of landscape evolution.

 

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